what causes Earthquakes?
- Forces and stresses along faults can build up as blocks of rock are pushed or pulled apart. If pressure becomes too great, the rocks break at weak points along the fault releasing energy
- Energy released from rocks breaking at weak points results in an earthquake.
What are the epicenter and the focus?
Focus - the point where the energy is released
Epicenter - The point on Earth’s surface directly above where the energy is released (Focus)
Epicenter - The point on Earth’s surface directly above where the energy is released (Focus)
- Energy that reaches the surface is greatest at this point
- Energy spreads outward in all directions as vibrations called seismic waves
Primary (P) Waves
•Compression Waves
•Travel the fastest out of the 3 types of waves
•Move through solid and liquid layers of Earth
- Push and pull rock creating a back and forth motion in the direction the wave is moving
•Travel the fastest out of the 3 types of waves
•Move through solid and liquid layers of Earth
Secondary (S) Waves
•Transverse Waves
•Move slower than primary waves
•Can only move through solid rock
- Move at right angles to primary waves causing rocks to move up and down and side to side
•Move slower than primary waves
•Can only move through solid rock
surface waves
Can cause the ground to shake making rock sway from side to side and roll like an ocean. These waves occur when wither a primary or secondary wave reaches the Earth's surface. Therefore, they can be compression or transverse waves and travel the slowest out of the types of waves.
How can we measure earthquakes?
A seismograph is a device used to record seismic waves. the device produces jagged lines that are a record of the shaking during an earthquake and also show the earthquake's intensity. The recording of jagged lines is called a seismogram.
Triangulation is a method of identifying the epicenter of an earthquake by using seismograph data from three (3) different locations and plotting that information on a map. Where all three circles intersect is the exact point of the epicenter of an earthquake. |